Dogs are mammals that belong to the family Canidae, such as wolves, foxes and coyotes. Usually, the term dog is used to mean the domestic dog (Canis familiaris), which is believed to be descended from a wolf-like ancestor. (Some scientists maintain that the domestic dog is a subspecies of wolf, Canis lupus familiaris.)

Dog societies are characterized by companionate hierarchy, in which each individual has a rank in society, and in which there is intense loyalty within the group. Dogs thrive in human society because their relationships with humans mimic their natural social patterns. The dog is always aware of its rank vis-a-vis other individuals in the group, and it may be noted that an assertive dog often considers itself the alpha animal, while considering its human owner to be subordinate.